The locator is leaking air
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This post was last edited by jzhwwdz on 2018-12-28 at 13:52. Many of the pneumatic control valves in our company use the type of actuator shown in the picture; each actuator produces a slight hissing sound due to air leakage, but some of them have a rather loud hissing sound. I don’t quite understand why there is this hissing sound
This is Metso’s intelligent valve positioner. After detecting the valve position, the microprocessor compares it with the set value, and then sends a signal to the piezoelectric valve in order to control the pneumatic slide valve or air source amplifier, ensuring a continuous supply of air pressure sufficient to drive the valve. So, by getting close to the locator, one can hear the airflow sound. That’s how it is under normal circumstances. There have also been cases of leaks; definitely the noise level was quite high.
Is there a manual for this? I’ve been looking for it for a long time but can’t find it
There are many problems with air leakage, but most of them are not related to the locator itself.
This post was last edited by jzhwwdz on 2018-12-29 09:08. Thank you for your reply. This type of locator is probably not intelligent. The DCS sets whatever opening degree, and that’s the opening degree at the site; there is no microprocessor in the positioner. Also, when there is airflow noise, these valves are in the closed state – does this situation occur as well at that time?
You’re welcome. This phenomenon can occur even if it is not a smart locator. The mechanical type measures the back pressure of the nozzle baffle; when it is in the middle position, air continuously flows out from the nozzle. The magnetic motor receives 4–20mA signals; when the detection mechanism detects an unbalanced torque, it pushes the baffle to move. When equilibrium is reached, the baffle stops moving. The gas is delivered to the diaphragm chamber of the control valve to reach the desired position.
In mechanical positioners, air leakage from the amplifier is a common occurrence and considered normal. Maintain the valve position in normal condition